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... this section, to simplify the dynamic equations, it is assumed that robot motion lies in a horizontal surface without obstacles. Therefore, to derive the dynamic equations, the action of suspension system would be neglected. Fig. 7 shows the masses and inertias of the robot. The robot is modeled as a set of three different rigid bodies. The robot chassis is illustrated as a triangle. Its mass m c contains the chassis, motors, battery, and all other parts rigidly attached to it, its moment of inertia with respect to the Z ́ axis is I z ́ , Its mass center is assumed to be located on the Z ́ axis. The three omni-wheels are same, with masses of m w . The mass center of the omni-wheels is located on their axis of rotation at the distance r R from the robot's center. Also, moments of inertia about the axis passing through their center and parallel to Z ́ axis and axis of rotation are I wz ́ and I wa , respectively. Also, the three ball wheels are the same, with masses of m s . their moments of inertia about principle axis of rotation is I s . The robot total mass m R consists of the chassis mass plus the wheels masses. Its center of mass is assumed to be located on the Z ́ axis at the height h above the ...
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Citations
... The proposed robot design solved the vibration and load capacity issues commonly encountered in ball wheel omni-directional robots. A similar research in [98], the diameter of the balls was modified to be larger in size to enable the robot to operate in outdoor environments. Additionally, a suspension system was added to the robot to improve its stability during movement. ...
This review paper provides a comprehensive comparison of various omni-directional mobile robots and their respective wheel types, motion systems, degrees of freedom, and field of applications. A summary of the advantages and disadvantages of each wheel type is presented, as well as the corresponding limitations. This paper also highlights the need for further research in several key areas, such as developing efficient and reliable control algorithms, exploring new materials and fabrication methods for wheel components, and investigating novel wheel designs. The insights and recommendations provided in this paper can serve as a valuable reference for designers and researchers seeking to improve the performance of omni-directional mobile robots in a variety of applications.
... [1]. Tech United Turtles [9] CAMBADA [10] [15] (Ns, Nw) = (3, 2) ...
Friction drive systems are adopted for many robots of spherical locomotion type. Such systems have problems, including traversing uneven surfaces, slipping of the roller, and dust between the sphere and the roller. Despite of the disadvantages, these systems attract attention because of the possibility of stepped climbing and omnidirectional locomotion. In the future, it is anticipated that the mechanism using the sphere are developed. When the kinematics with respect to multiple rotational axes in arbitrary contacted on the sphere is clarified, the mechanism may be widely used. In the paper, a general theorem for kinematics is discussed including the number of rollers driving the sphere, the type of roller (constraint or unconstraint), and the contact points of the rollers on the sphere and the roller axes direction. To verify the validity of the kinematics model a locomotion model of the ball dribbling mechanism with the two rollers is presented as a special example by carrying out the experimental demonstration using the device robot.
... The continuous isotropic surface geometry of spherical wheels makes them an ideal choice for enabling unconstrained holonomic ground motion. While ball driven mobility platforms are a relatively new and emerging class for vehicle locomotion, renewed interest in research literature [1][2][3][4][5][6][7] has shown that they can exhibit agile omnidirectional maneuvering capabilities that are difficult or impossible to achieve using standard fixed or steered wheels. Spherical wheels also exhibit better ground traversal performance compared to other types of specialized wheels such as Omni-wheels and Mecanum wheels [8]. ...
... Existing implementation of ball driven mobility platforms found in literature include dynamically stable Ballbots [1,2] as well as statically stable multi-ball mobility platforms that utilize three or more spherical wheels [4,3,5]. An example of a traction ball drive used for a holonomic multi-ball mobility platform from the authors' prior work is shown in FIGURE 1. ...
Ball-driven mobility platforms have shown that spherical wheels can enable substantial freedom of mobility for ground vehicles. Accurate and robust actuation of spherical wheels for high acceleration maneuvers and graded terrains can, however, be challenging. In this paper, a novel design for a magnetically coupled ball drive is presented. The proposed design utilizes an internal support structure and magnetic coupling to eliminate the need for an external claw-like support structure. A model of the proposed design is developed and used to evaluate the slip/no-slip operational window. Due to the high-dimensional nature of the model, the design space is sampled using randomly generated design instances and the data is used to train a support vector classification machine. Principal component analysis and feature importance detection are used to identify critical parameters that control the slip behavior and the feasible (no-slip) design space. The classification shows an increase in the feasible design space with the addition of, and increase in, the magnetic coupling force. Based on the results of the machine learning algorithm, FEA design tools and experimental testing are used to design a spherical magnetic coupler array configuration that can realize the desired magnetic coupling force for the ball drive.
... network was able to maintain this frame rate for the majority of the time with the exception of 5 specific instances where a drop in the network bandwidth resulted in a drop in the frame rate or a loss of the network connection. For the first three instances (which occurred at approximately 25 seconds,125 seconds, and 190 Average frame rate: 21.1 fps Standard deviation: 1.18 fps Minimum frame rate: 15.3 fps Constant adjustments to video compression quality is made by controller in response to network bandwidth variability Constant adjustments to MRGC resolution level is made by controller in response to network bandwidth variability Average δt: 0.049 seconds Standard deviation: 0.016 seconds Maximum δt: 0.41 sec Large jumps in compression quality correspond to remapping of compression quality range for new MRGC level as shown in ...
... [1] describes the first two examples of ball drives where the wheel rests against rollers mounted around a tilted ring. [2,3,4] describe schemes where the wheel is driven by an omni-wheel in one axis and is free to rotate in the remaining axes. In [5] and [6,Tribolo robot], the wheel is driven by a roller located on its horizontal great circle, allowing it to rotate freely around the horizontal axis orthogonal to the driven axis. ...
... The proposed ball drive was implemented in the widely used 3-wheel configuration (same kinematics as [2,3,5]), 2 Using components described in Section III: Pm,w = 1.232N, as seen in Figure 6. In such scales, the natural placement of the motor on the side of the ball wheel allows a compact arrangement of the components (also mentioned by [5]). ...
... Additionally, the omniwheel drive was visually observed to vibrate significantly more compared to the ball drive due to discontinuous contact points with the ground, as predicted by the literature (e.g. [2,3,7,8]). As mentioned previously, the proposed ball drive design also tends to be more geometrically compact (both horizontally and vertically) compared to a kinematically equivalent omniwheel drive design. ...
We present an omnidirectional ball wheel drive design that utilizes a permanent magnet as the drive roller to generate the contact force. Particularly interesting for novel human-mobile robot interaction scenarios where the users are expected to physically interact with many palm-sized robots, our design combines simplicity, low cost and compactness. We first detail our design and explain its key parameters. Then, we present our implementation and compare it with an omniwheel drive built with identical conditions and similar cost. Finally, we elaborate on the main advantages and drawbacks of our design.
... Vrunda et al. (2010) analysed a spherical-wheeled mobile robot rolling on a plane for feasible path planning and feedback control algorithms. Ghariblu et al. (2011) implemented an OWMR using three spherical wheels driven by classical omni-wheels. Chen et al. (2012) presented an omnidirectional spherical robot, called Omnicron. ...
Omnidirectional wheeled mobile robots (OWMRs) have gained increasingly popularity because they can move into any direction, while their orientation can be pointed to any angles. Thus, the aims of this paper are to update a literature review of OWMRs and to categorise interesting research papers according to wheel types, wheel arrangements, and their practical applications. Wheel types are divided into special omnidirectional wheels and steerable conventional wheels. Advantages and disadvantages of each type of OWMRs are also pointed out in order to help robotic designers to choose an appropriate wheel mechanism. Then, practical applications are presented to show the usefulness of OWMRs.
... Several solutions exist in the literature such as: the "offset caster wheels" [25], [26], the "split offset caster wheel" [27], [28]. Comparatively, special wheels were developed and/or used as the "universal wheels" [29]- [31], "orthogonal spherical wheels" [32], [33], and "ball wheel" [34]. ...
This paper presents the design and the implementation of a new platform for balance analysis. The designed platform called IsiSkate is an omnidirectional mobile robot. It is specially designed to reproduce the perturbation of a public transportation in a laboratory environment. It is equipped with force and inertial sensors intended for the evaluation of human posture for static and dynamic equilibrium analysis of a human subject standing on it. This platform is able to disturb the balance of a human weighing 120 kg with an acceleration of 3 m/s $^{2}$, which is above the safe limit 1.9 m/s $^{2}$ in public transportation. The platform is capable of measuring in real time the displacement of the center of pressure independently for the left and right foot at baud rate of 100 Hz. With its integrated inertial sensor, the platform is also capable of estimating the displacement of center of mass of the human subject as well as the motion of the ankle, knee, and hip joint. In this paper, we give a description of the mechanism that constitutes the platform. Technical specifications of electrical and computer architecture are given. Some tests with a subject were carried out to assess the performance of this new platform. Some results from the stability analysis based on the model of an inverted pendulum are also presented in this paper.
... "Ball wheel" proposée dans (Ghariblu et al., 2011). Malheureusement les solutions citées n'offrent pas la compacité suffisante pour répondre aux contraintes technologiques qui nous ont été imposées. ...
In this thesis, we achieved the development of a robotic system to reproduce in laboratory all the disturbances undergone by a human subject in public transport in order to make an analysis of postural balance. Reproductive simulated disturbances in laboratory require developing a dynamic platform unconstrained in its movement. Analysis of postural balance also requires the development of an inverted pendulum model to define quantitative indices of stability and to make comparative and statistical analysis. According the objectives of this research work, we realized a compact omnidirectional mobile platform capable of supporting a weight of about 120kg. This platform gives the subject placed on it a better perception of comfort and safety. Its performances in terms of trajectory tracking and acceleration control are carried out and evaluated. These performances are very satisfactory compared to experiments in the subway since the produced accelerations are higher than the values required by this means of transport. Thus, the platform is able to reproduce the perturbation compatible with the subway. We proposed two methods of analysis based on triaxial accelerometers connected and synchronized platform for evaluating torque and joint position of the ankle, knee and hip of the subject. The results obtained are comparable to those obtained by more expensive motion capture system with biomechanical software. New postural balance indices have been proposed from the biomechanical parameters of 22 subjects. These indices can be used by therapists to analyze and predict the ability of maintaining the balance of a passenger in the subway or more generally in public transport.
... In contrast, ball wheel mechanisms provide continuous contact and thus do not cause any vibrations. Various examples of mobile robot platforms based on ball-wheel units have been presented [11] [12]. West and Asada [13] identified two generic types of arrangements for omnidirectional ball units, only one of which allows free rotation with at least two DOFs as well as provides closure around the ball so as to capture it. ...
Omnidirectional mobile robots offer interesting features for industrial and service applications, in particular, when operating in tight spaces. Compared to car-like nonholonomic vehicles, they provide a higher degree of maneuverability, and often require less complex path planning and control schemes. Three different types of holonomic wheels that enable omnidirectional motion have been proposed in literature: universal, Mecanum, and ball wheel mechanisms. A problem commonly associated with the first two wheel types is that they induce vibrations in the system due to the discontinuous contact points. In this article, a ball wheel mechanism with superior features including slip detection, free-wheel modus and attrition sensing is presented. The first prototype was built using additive manufacturing of polypropylene. The requirements for such a design are discussed. Based on the ball wheel drive presented in this article, a design for an omnidirectional mobile robot platform driven by three redundant ball wheel units is proposed. The velocity kinematic model of this mobile base is also addressed.
Installing and removing ground wires is a common substation switch operation. However, due to the high installation position of the substation equipment, the position of the grounding point is mostly high, and the grounding line has a large cross-sectional area, long length and heavy weight. It is often difficult to complete the connecting work because of the insufficient rigidity of the operating rod when it is directly connected to the ground by using the operating rod. Because of the heavy grounding wire itself and the long insulating rod, the operators on the spot stand on the herringbone ladder to carry out the hanging and dismantling operation, which is time-consuming and labor-consuming. To solve the above problem, this paper will develop a mobile operating platform technology suitable for substation complex road conditions, and applicable to substation folding and telescopic mixing robot hanging grounding wire lifting work platform technology, and based on intelligent control system substation robot multi-sensor information fusion technology. Developed an automatic hanging grounding wire robots for the voltage level below 500 kV, ensure the personal safety of operators, improve the intelligent level of substation operation.
